x^2+2xy+y^2-a(x+y)+25是完全平方公式,求a的值

(-x-y)(x^2+xy+y^2) 化简x^-y^/x^-2xy+y^ 2*(x-y)²(y-x)(xy) （x^2+xy/x-y)/（xy/x-y)计算 X-Y/2X+2Y XY/X+Y² 因式分解：x×x-xy-2y×y-x-y 因式分解（x+y-2xy)(x+y-2)+(xy-1)^2设x+y=a,xy=b, 因式分解:12xy^2(y-x)+xy^3(x-y)+4x^2y(x-y) (x-y)[(x+y)^2-xy]+(x-y)[(x-y)^2+xy] .(x+y-2)(x+y-2xy)+(xy-1)^2 (x^2-xy)y÷y-x/xy怎么做? 代数 x^-y^/ x^-(y-z)^ 除以 x^+2xy+y^/(x-y)^-z^ 乘 x^+xy-xz/x^-xy (x+y)/x /(x-(2xy-y^2)/x) 因式分解 x^2-xy/xy-y^2约分 （y/(x^2-xy)+x/(y^2-xy))除以(x-y)/(xy) (x+y)(x+y+2xy)+(xy+1)(xy-1)(x+y)(x-y)+4(y-1) x^2y-2xy+y化简 X^Y-2XY^2+y^3